Recovery techniques in mobile networks

ABSTRACT

A technique for protecting location information of a subscriber in a mobile network is disclosed. A User Mobility Server (UMS) receives a first query from a first call state control function (CSCF). The UMS transmits a call setup and a subscriber identity to a servicing-call state control function (S-CSCF). The S-CSCF may have no record of the subscriber identity due to a restart are some other event. The UMS receives a second query from the S-CSCF based in part of the subscriber identity. The UMS transmits a home address of a mobile station to the S-CSCF. The UMS may also transmit a profile download to the S-CSCF.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.13/097,709, filed Apr. 29, 2011, which is a Continuation of U.S. patentapplication Ser. No. 12/720,862, filed Mar. 10, 2010, which is aDivisional of U.S. patent application Ser. No. 09/802,861, filed Mar.12, 2001, (now U.S. Pat. No. 7,769,374), each of which are incorporatedherein by reference in their entirety.

FIELD

The present disclosure relates to recovery techniques for use in mobilenetworks. More particularly, the present disclosure relates toprotecting the Transport Address (TA) which is a current Care of Addressof a mobile subscriber is reachable from loss and after Call StateControl Function (CSCF) crashes and after reset situations of a networkelement realizing CSCF functionality.

DESCRIPTION OF RELATED ART

Technical Report TR 23.821 V1.0.1, published July 2000 by the 3rdGeneration Partnership Project (3GPP) and available on the Internet athttp://www.3gpp.org, discloses the specifications of a 3G All-IP mobilenetwork and this report is incorporated by reference herein in itsentirety.

FIG. 1 illustrates the architecture of the network disclosed in theabove-noted Technical Report. The elements shown with asterisks areelements which have been duplicated for figure layout purposes only.These duplicated elements belong to the same logical element in thereference model.

Unfortunately, the network disclosed in the Technical Report fails toinclude any protection of the TA of a 3G All-IP subscriber from loss.Furthermore, the network disclosed in the Technical Report fails toprotect the IP address of a subscriber in the case of a reset situationof a network element realizing CSCF functionality, that is, a CSCF,thereby preventing recovery after a reset of the network element. Stillfurthermore, the network disclosed in the Technical Report fails toprotect the location information of a subscriber after a CSCF crash,thereby preventing recovery after a CSCF crash.

SUMMARY

An object of the present disclosure is to provide a technique forrecovering location information of a subscriber in a mobile networkincluding forwarding a registration request from the subscriber to anS-CSCF including the subscriber's TA and then forwarding an AL(Application Level) location update from the S-CSCF to a Home SubscriberServer (HSS) including the subscriber's TA and the (S-CSCF) address andstoring data including the subscriber's TA and the S-CSCF address in theHSS so as to be protected against loss.

Another object of the present disclosure is to provide a technique forrecovering location information of a subscriber in a mobile networkincluding forwarding a registration request from the subscriber to anS-CSCF including the subscriber's TA and then forwarding an AL locationupdate from the S-CSCF to an HSS including the S-CSCF address andstoring data including the subscriber's TA in a non-volatile memory ofthe S-CSCF so as to be protected against loss.

Yet another object of the present disclosure is to provide a techniquefor recovering location information of a subscriber in a mobile networkincluding upon an S-CSCF receiving a call setup request for thesubscriber from an Interrogating Call State Control Function (I-CSCF),forwarding a route request to a User Mobility Server (UMS) and receivinga home address of the subscriber and then forwarding the call setuprequest from the S-CSCF to a home agent at the home address of thesubscriber and then forwarding the call setup request from the homeagent to the subscriber and subsequently forwarding an address updatefrom the subscriber to the S-CSCF.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and a better understanding of the present disclosure willbecome apparent from the following detailed description of exampleembodiments and the claims when read in connection with the accompanyingdrawings, all forming a part of the disclosure of this disclosure. Whilethe foregoing and following written and illustrated disclosure focuseson disclosing example embodiments of the invention, issued a clearlyunderstood that the same is by way of illustration and example only andthe invention is not limited thereto. The spirit and scope of thepresent invention are limited only by the terms of the appended claims.

The following represents brief descriptions of the drawings, wherein:

FIG. 1 illustrates the architecture of a 3G All-IP mobile network.

FIG. 2 illustrates reaching a called party after losing LA (LocationArea) information in a legacy mobile network.

FIG. 3 illustrates failure to reach a called party after losing TAinformation in a 3GPP All-IP mobile network.

FIG. 4A illustrates sending subscriber TA to S-CSCF and then forwardingit to HSS at registration.

FIG. 4B illustrates an example of reaching a called party after losingTA information in a mobile network in accordance with the presentdisclosure.

FIG. 5 illustrates the signal flow in the case of a recovery after aCSCF crash in accordance with another embodiment of the presentdisclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before beginning a detailed description of the subject disclosure,mention of the following is in order. When appropriate, like referencenumerals and characters may be used to designate identical,corresponding, or similar components in differing drawing figures.Furthermore, in the detailed description to follow, examplesizes/models/values/ranges may be given, although the present inventionis not limited thereto. Lastly, other components may not be shown withinthe drawing figures for simplicity of illustration and discussion and soas not to obscure the invention.

In the application level of a 3G All-IP network, the reachability of asubscriber is maintained in two levels, namely, the network elementlevel and the subscriber level. The S-CSCF that the subscriber iscurrently registered to and the TA of the roaming subscriber, which thesubscriber provides to the network during Application Level (AL)registration, must be known to and maintained by the network.

Without specific support for mobility in IPv6, packets destined to amobile subscriber would not be able to reach it while the subscriber isaway from its home link (the link on which its home IPv6 subnet prefixis in use), since routing is based on the subnet prefix in a packet'sdestination IP address. In order to continue communication in spite ofits movement, a subscriber could change its IP address each time itmoves to a new link, but it would then not be able to maintain transportand higher-layer connections when it changes location.

Mobile IPv6 allows a subscriber to move from one link to another withoutchanging its IP address. A subscriber is always addressable by its “homeaddress”, an IP address assigned to it within its home subnet prefix onits home link. Packets may be routed to the subscriber using thisaddress regardless of its current point of attachment to the Internet,and it may continue to communicate with others after moving to a newlink. The movement of a subscriber away from its home link is thustransparent to transport and higher-layer protocols and applications.

A mobile subscriber is always addressable by its home address, whetherit is currently attached to its home link or is away from home. While itis at home, packets addressed to its home address are routed to it usingconventional Internet routing mechanisms in the same way as if it werenever mobile. Since the subnet prefix of its home address is the subnetprefix (or one of the subnet prefixes) on the subscribers' home link (itis the mobile subscribers' home subnet prefix), packets addressed to itwill be routed to its home link.

While a subscriber is attached to some foreign link away from home, itis also addressable by one or more care-of addresses, in addition to itshome address. A care-of address is an IP address associated with amobile node while the subscriber is visiting a particular foreign link.The subnet prefix of a subscriber's care-of address is the subnet prefix(or one of the subnet prefixes) on the foreign link being visited by it;if it is connected to this foreign link while using that care-ofaddress, packets addressed to this care-of address will be routed to thesubscriber in its location away from home.

The association between a subscriber's home address and care-of addressis known as a “binding” for the subscriber. It typically acquires itscare-of address through stateless or stateful Address Autoconfiguration,according to the methods of IPv6 Neighbor Discovery. Other methods ofacquiring a care-of address are also possible, such as staticpreassignment by the owner or manager of a particular foreign link, butdetails of such other methods are beyond the scope of this discussion.

While away from home, a mobile subscriber registers one of its care-ofaddresses with a router on its home link, requesting this router tofunction as the “home agent” for it. This binding registration is doneby the subscriber sending to the home agent a packet containing a“Binding Update” destination option; the home agent then replies to thesubscriber by returning a packet containing a “Binding Acknowledgment”destination option. The care-of address in this binding registered withits home agent is known as the subscriber's “primary care-of address”.The subscribers' home agent thereafter uses proxy Neighbor Discovery tointercept any IPv6 packets addressed to the subscribers' home address(or home addresses) on the home link and tunnels each intercepted packetto the subscribers' primary care-of address. To tunnel each interceptedpacket, the home agent encapsulates the packet using IPv6 encapsulation,with the outer IPv6 header addressed to the subscribers' primary care-ofaddress.

Keeping the address of the S-CSCF ensures that a call to a subscribercan be routed to the destination node, that is, the S-CSCF. Keeping thecurrent TA of the subscriber ensures that a call made to the subscriberwhich arrives at the S-CSCF can finally reach the subscriber.

As illustrated in FIG. 2, in legacy mobile networks, such as GSM, theinformation on the serving MSC/VLR (stored in the HLR) is adequate. Thatis, the called party can be reached even after the loss of thesubscriber location area (LA) information by a searching/pagingmechanism. In step 1, the current V-MSC/VLR for a called party is firstlocated and in step 2 a setup toward the V-MSC/VLR is. performed. Instep 3, upon a loss of the LA information, the called party is paged inall cells under the V-MSC/VLR.

On the other hand, as illustrated in FIG. 3, in the 3G All-IP network,no such searching mechanism is available, so that the information of thecurrent S-CSCF (stored in the HSS) is insufficient to reach thesubscriber upon the loss of the subscriber TA. In step 1, S-CSCF islocated and in step 2 a setup toward the S-CSCF is performed. However,in step 3, in the absence of the TA of the called party, the calledparry is not reachable.

The applicants have determined that the TA of a 3G All-IP subscribershould be protected against loss with the same level of security as thatfor the Serving CSCF (S-CSCF). The applicants have proposed options toprotect the TA of a subscriber, namely, one option in which the TA isforwarded to the HSS and another option in which there is a securitybackup of the TA within the CSCF. The TA of the subscriber should beforwarded to the HSS at registration and downloaded from the HSS to theS-CSCF during recovery. Still another option is to have a permanent IPv6(Internet Protocol Version 6) address allocated to the subscriber and tohave the subscriber update its current Care-of Address (part of the TA)to the Home Agent upon obtaining the current TA.

As noted above, in accordance with the present disclosure, variousoptions are available for implementing protection and recovery of thesubscriber TA.

In the first option, as illustrated in FIG. 4A, “a safe copy” of thesubscriber's TA is forwarded to the HSS for storage and protection. TheTA must enjoy the same level of protection against loss as the S-CSCFaddress. The TA and other data can then be restored to the S-CSCF uponthe earlier loss of the data by the S-CSCF. It is noted that thesubscriber's TA is stored in the S-CSCF for normal operation. Anincoming call from an REP (Remote End-Point) is received by the S-CSCFin step 1. In step 2, the S-CSCF looks for the subscriber's TA so as toroute the call but fails to find the subscriber's TA. In step 3, theS-CSCF initiates the restoration of the subscriber's TA (and possiblyother data) from the HSS. This option is only available when the S-CSCFloses only the TA of the subscriber. Finally, in step 4, the call isthen routed to the subscriber using the recovered TA.

As illustrated in FIG. 4B in step 1, the registering subscriber forwardsan AL registration request to the S-CSCF including the TA. In step 2, anAL Location Update is forwarded to the HSS including the TA and S-CSCFaddress. In step 3, the HSS stores the updated TA and S-CSCF address (ina hard disk, for example, or other non-volatile memory). In step 4, theHSS forwards an AL Location Update acknowledgement to the S-CSCF whichstores the TA and subscription profile and other data in step 5. In step6, the S-CSCF forwards an AL registration acknowledge to the registeringsubscriber.

In the second option, the same level of protection against loss appliesfor the subscriber's TA stored in the S-CSCF as that of the S-CSCFaddress stored in the HSS. For example, the subscriber's TA can bebacked up in a hard disk, or other non-volatile memory in the S-CSCF.

In the case of an S-CSCF crash, when the S-CSCF restarts, all of theinformation regarding the mobile subscribers registered with it,including the information on how to reach the mobile subscribers, islost. In such a situation, it is not possible to deliver mobileterminated calls to the mobile subscribers that were registered with theS-CSCF that was restarted.

In providing a solution to the above-noted problem in accordance withthe third option, the following assumptions are made:

1) IPv6 is adopted for IP addressing and a subscriber is given a homeaddress at subscription time. This home address is stored in a UMS.

2) The subscriber is in an area assigned to an S-CSCF and has registeredwith it and has provided its' TA, that is, the current address where thesubscriber is reachable. Such an address is not the static home addressbut rather is the Care-of Address. Whenever the S-CSCF has to forwardsignaling to the mobile subscriber, it uses the Care-of Address. Thesubscriber has also registered its current Care of Address with its HomeAgent.

3) The S-CSCF restarts due to a fault and loses the information aboutthe mobile station.

The following procedure in accordance with the present disclosure, asillustrated in FIG. 5, may, for example, be used for mobile terminatingcall delivery when, as illustrated in 1, the S-CSCF crashes andrestarts, the S-CSCF has no memory of what mobile stations (MSs) wereregistered with the S-CSCF and does not have any of the MSs Care ofAddress addresses:

When an incoming call at 2 reaches a CSCF in the home network, eitherfrom another IP based terminal or from an MGCF (Media Gateway ControlFunction), the I-CSCF queries at 3 the UMS based on the alias dialed bythe calling party.

During registration, the UMS has stored information about the S-CSCF andinformation as to how the mobile subscriber can be reached. Moreparticularly, the UMS has stored the address of the S-CSCF, that is, theaddress where CC (Call Control) signaling must be forwarded. At thispoint, two scenarios are possible:

The information in the UMS regarding the S-CSCF is still valid; the UMSreturns at 4 the address of the S-CSCF and the Subscriber Identity andthen forwards the call setup 5 to the S-CSCF.

The S-CSCF, not having information available for the alias to which thecall corresponds due to a crash, queries 6 the UMS based on theSubscriber Identity optionally indicating that a restart took place inorder to trigger a profile download.

The UMS returns at 7 the Home Address of the MS to the S-CSCF.

The S-CSCF forwards at 8 the signaling to the Home Address which is thehome agent.

The home agent receives the packets at 9 and forwards them at 10 to theMS using the Care of Address obtained during the Mobile IP signalingexchanged when the Care-of Address was created (the usual procedure inMobile IP).

When the MS receives the first packet, it sends at 11 a message to theS-CSCF which sent the packet to update the address indicating the Careof Address as the correct address to be used to reach the subscriber(the usual procedure in Mobile IP) and call control signalling is sentat 12 from the S-CSCF to the MS.

When the call is terminated the subscriber can optionally re-registerwith the S-CSCF.

2) The information in the UMS is not valid; the UMS returns the HomeAddress of the mobile subscriber.

The I-CSCF forwards the signaling to the Home Address.

The Home Agent receives the packets and forwards them to the Care-ofAddress obtained during the Mobile IP signaling exchanged when theCare-of Address was created (the usual procedure in Mobile IP).

When the mobile subscriber receives the first packet, it sends a messageto the I-CSCF which sent the packet to update the address indicating theCare of Address as the correct address to be used to reach thesubscriber (the usual procedure in Mobile IP).

When the call is terminated the subscriber can optionally re-registerwith a S-CSCF.

This concludes the description of the example embodiments. Although thepresent invention has been described with reference to a number ofillustrative embodiments, it should be understood that numerous othermodifications and embodiments can be devised by those skilled in the artthat will fall within the spirit and scope of the principles of thisinvention. More particularly, reasonable variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the foregoing disclosure,drawings, and appended claims without departing from the spirit of theinvention. For example, the example embodiments of the present inventionhave been described with respect to currently used networks, such as 313All-IP mobile networks, and standards for simplicity. It is, of course,understood that the present invention is not limited thereto. Inaddition to variations and modifications in the component parts and/orarrangements, alternative uses will also be apparent to those skilled inthe art.

1. A method comprising: receiving a call for a subscriber at a firstserver, wherein the call for the subscriber comprises a dialed alias;sending a route request from the first server to a mobile server,wherein the route request includes the dialed alias; receiving aresponse at the first server from the mobile server, wherein theresponse comprises an address of a second server and a subscriberidentity; and sending a call setup request from the first server to thesecond server, wherein the call setup request comprises the subscriberidentity and the dialed alias.
 2. The method of claim 1, wherein thefirst server comprises an Interrogating-Call State Control Function(I-CSCF).
 3. The method of claim 1, wherein the second server comprisesa Server-Call State Control Function (S-CSCF).
 4. The method of claim 1,wherein the sending a route request comprising querying the mobileserver based on the dialed alias of the subscriber.
 5. The method ofclaim 1, further comprising receiving an identity of the subscriber atthe first server from the mobile server.
 6. The method of claim 1,wherein sending a route request comprises querying the mobile serverbased on the dialed alias.
 7. A system comprising: a first serverconfigured to: receive a call for a subscriber, wherein the call for thesubscriber comprises a dialed alias; send a first route request to amobile server, wherein the first route request includes the dialedalias; receive a response from the mobile server, wherein the responsecomprises an address of a second server and a subscriber identity; andsend a call setup request to the second server, wherein the call setuprequest comprises the subscriber identity and the dialed alias.
 8. Thesystem of claim 7, wherein the second server is configured to: receivethe call setup request for the subscriber; send a second route requestto a mobile server, wherein the route request comprises the subscriberidentity; receive a home address of the subscriber from the mobileserver; and send the call setup request to a home agent at the homeaddress of the subscriber.
 9. The system of claim 8, wherein the firstserver is further configured to query the mobile server based on analias of the subscriber which was dialed by a party that sent the call.10. The system of claim 8, wherein the first server is furtherconfigured to receive an identity of the subscriber from the mobileserver.
 11. The system of claim 8, wherein the call setup requestincludes the identity of the subscriber.
 12. The system of claim 8,wherein the second server is further configured to query the mobileserver based on the identity of the subscriber.
 13. The system of claim8, wherein the second server is further configured to send the callsetup request to a care of address of the subscriber.